Yes, I had 6 out of 6 visible, only the first five show. I tried disabling the smart calendar called "Birthdays" and the local calendar "Private" as it has no entries, meaning 4 are visible of the 6. The last one still does not show, even though it is ticked...

I now have the following
Birthdays (smart, 4 events) Not visible
N900 (Synchronised, 145 events) Visible
Photography (Local, 25 events) Visible
Private (Local, 0 events) Not visible
Scouts (Local, 20 events) Visible
Work (Local, 4 events) Visible

I recently added Work as I start a new job next week. My first event in that calendar is tomorrow, but nothing shows on the widget. I changed one of the timed events in "Work" calendar to an all day event to see if it would show, but it does not. I also tried renaming the calendar incase of some internal name conflict but it made no difference either...